<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>基础选择器</title>
    <style>
        div{
            color: blue;
        }
        .bg{
            background-color: blueviolet;
        }
        #span-id{
            border: 3px;
            background-color: blueviolet;
        }
        .div2{
            background-color: brown;
        }
        .box{
            font-size: 2em;
        }
    </style>
</head>
<body>
    <!-- 标签选择器 -->
     <div>div1</div>
     <!-- 类选择器 -->
     <h1>h1</h1>
     <div class="bg">div</div>
     <p>p</p>
     <span id="span-id">span</span>
     <div class="div2"> 这是div</div>

</body>
</html>